Trophic modes of large Antarctic Foraminifera: roles of carnivory, omnivory, and detritivory

Astrammina rara, Crithionina delacai, and Notodendrodes hyalinosphaira are 3 of the largest and most abundant members of the foraminiferal assemblage at a shallow-water (28 to 32 m) site in Explorers Cove, Antarctica. This study summarizes observations from 2 decades of research, during which we employed laboratory-based feeding experiments and fatty acid biomarker analysis to characterize trophic dynamics and ecological roles of the 3 species, In feeding experiments, A. rara consumed a variety of co-occurring metazoans (several Crustacea, Mollusca, Echinodermata, and a Nephtys species). C. delacai, N. hyalinosphaira, and a number of other foraminiferal species from Explorers Cove successfully trapped Artemia sp. nauplius prey in a setup designed to examine the efficiency of prey capture. Fatty acid analyses on samples from early (November 7, 2001) and late (January 31, 2002) austral summer revealed that the 3 species contained substantial amounts (33 to 45.5%) of polyunsaturated fatty acids (PUFAs), which are produced by microalgae, indicating the downwards transfer of carbon from sea-ice associated primary production. In the case of A. rara, this may be due to the ingestion of herbivorous metazoa, rather than direct uptake of microalgal material. A. rara contained significantly (p < 0.05) higher amounts of the zooplankton biomarkers 20:1(n-9) and 22:1(n-11), and C. delacai contained more PUFAs early, compared to late, in the season. Two morphotypes of N. hyalinosphaira had different fatty acid Profiles, indicating distinct trophotypes. Our results illustrate specific adaptations to different trophic resources in these protists, and they demonstrate the potential impact that large carnivorous species of Foraminifera may have on the structure of benthic communities where they are abundant

The role of foraminifera in Antartic Benthic communities with respect to the seasonal deposition of organic matter

Antarctic marine environments are characterised by intense seasonality. High nutrient concentrations in seasonally ice covered Antarctic coastal and shelf areas lead to a massive phytoplankton bloom following the melting of the sea ice in spring and early summer. A major part of this particulate organic material can be deposited on the seafloor, where it is available as food for the benthic community. The seasonality of nutrient input is probably the most significant ecological feature in Antarctic shelf environments. Foraminifera often represent a substantial proportion of the abundance and biomass of benthic communities in polar environments, where they may contribute significantly to the benthic carbon cycle.  The Antarctic Peninsula shelf, with its regular seasonal phytoplankton blooms and following organic matter deposition, represents a good opportunity to investigate the influence of pulsed food input on the benthic community and the role of foraminifera in these environments.  This study examines benthic-pelagic coupling processes with a focus on foraminiferal and metazoan abundance and vertical distribution patterns at a study site on the Western Antarctic Peninsula shelf (FOODBANCS site A, 65°10’S, 64°46’W, near Anvers Island). In addition, aspects of foraminiferal feeding biology with respect to seasonal organic matter availability are investigated at three different sites around the Antarctic (Antarctic Peninsula shelf: FOODBANCS site A, Arthur Harbor: Anvers Island, Explorers Cove: McMurdo Sound), using fatty acid biomarker analysis, and the possible implications of the highly selective feeding displayed by some common species of foraminifera on Antarctic benthic communities are discussed. The results demonstrate that foraminifera and metazoans may respond in different ways to seasonal deposition of phytodetritus on the seafloor, and that foraminifera must be considered when studying benthic-pelagic coupling processes.  Furthermore, it is important to consider different species of foraminifera individually in ecological studies, rather than treating them as a single trophic entity.</p

The role of foraminifera in Antarctic benthic communities with respect to the seasonal deposition of organic matter

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Antarctic benthic foraminfera facilitate rapid cycling of phytoplankton-derived organic carbon

Fatty acid biomarker analyses of Cassidulina crassa, a dominant calcareous foraminieran at 55-m water depth in Arthur Harbor, Anvers Island (64°46′S, 64°04′W), Antarctica, revealed that this species responds rapidly to the deposition of fresh phytoplankton material from the overlying water column. During the sampling period in January/February 2002, a late summer phytoplankton bloom was clearly reflected in the fatty acid composition of C. crassa. This was apparent in the significant short-term increase of the relative content in polyunsaturated fatty acids, which more than doubled within the short period of one week from just over 14% on 28/29 January to 32% on 6 February. C. crassa feeds selectively on the high quality part of deposited organic matter, is highly abundant and widely distributed around the Antarctic, and has a wide bathymetric range. The present study shows that this species, like other, similar Antarctic benthic foraminiferal species such as Globocassidulina subglobosa, plays an important role in the rapid cycling of phytoplankton-derived organic carbon in Antarctic marine environments

Selective feeding by benthic foraminifera on phytodetritus on the western Antarctic Peninsula shelf: evidence from fatty acid biomarker analysis

This study presents the first direct evidence, based on biochemical analysis of fresh material, that certain benthic foraminifera feed selectively on specific components of seasonally deposited phytodetritus in their natural environment. Three abundant species of benthic foraminifera, the calcareous species Globocassidulina subglobosa and Quinqueloculina seminula and the agglutinated species Thurammina albicans, collected after the deposition of phytoplankton bloom material at a shelf site (560 m water depth) west of the Antarctic Peninsula in March 2001, showed significant differences in their fatty acid profiles compared to the surrounding phytodetritus. Furthermore, the 2 calcareous species contained significantly higher amounts of polyunsaturated fatty acids (PUFAs) than were found in their presumptive phytodetrital food source, indicating that the foraminifera discriminate between, and selectively feed on, the different components of the deposited material. Possible implications for the benthic food web are discussed

Political offensiveness in the mediated public sphere: The performative play of alignments

This chapter explores developing concerns about the rise of offensiveness in the political public sphere and more especially in social media. We argue that current iterations of purposeful political offence should be considered in the context of a number of factors. The first of these is a rise of “post-truth” politics (Montgomery, 2017), in which impressions of personal authenticity take the place of facts and truth becomes less important than ‘speaking your mind’. The second factor is the ascendency of short-form social media such as Twitter and Instagram, which disperse and fragment the discourse of political elites in a setting in which particular “authentic” styles prevail and in which relatively unrestricted access enables multi-articulated tactics of address. The chapter explores how examples of offensiveness in the agonistic political domain (see Ong) may have similar qualities to those “ritual insults” identified by Labov (1972), arguing, indeed, that like Labov’s examples they have a doubly-articulated quality. In the public sphere, however, they can rehearse the core beliefs of a supporting ingroup, and choreographing expressions of alignment for them, while at the same time offensively provoking an “offended” outgroup.

Measurements of the Total and Differential Higgs Boson Production Cross Sections Combining the H??????? and H???ZZ*???4??? Decay Channels at s\sqrt{s}=8??????TeV with the ATLAS Detector

Measurements of the total and differential cross sections of Higgs boson production are performed using 20.3~fb$^{-1}$ of $pp$ collisions produced by the Large Hadron Collider at a center-of-mass energy of $\sqrt{s} = 8$ TeV and recorded by the ATLAS detector. Cross sections are obtained from measured $H \rightarrow \gamma \gamma$ and $H \rightarrow ZZ ^{*}\rightarrow 4\ell$ event yields, which are combined accounting for detector efficiencies, fiducial acceptances and branching fractions. Differential cross sections are reported as a function of Higgs boson transverse momentum, Higgs boson rapidity, number of jets in the event, and transverse momentum of the leading jet. The total production cross section is determined to be $\sigma_{pp \to H} = 33.0 \pm 5.3 \, ({\rm stat}) \pm 1.6 \, ({\rm sys}) \mathrm{pb}$. The measurements are compared to state-of-the-art predictions.Measurements of the total and differential cross sections of Higgs boson production are performed using 20.3  fb-1 of pp collisions produced by the Large Hadron Collider at a center-of-mass energy of s=8  TeV and recorded by the ATLAS detector. Cross sections are obtained from measured H→γγ and H→ZZ*→4ℓ event yields, which are combined accounting for detector efficiencies, fiducial acceptances, and branching fractions. Differential cross sections are reported as a function of Higgs boson transverse momentum, Higgs boson rapidity, number of jets in the event, and transverse momentum of the leading jet. The total production cross section is determined to be σpp→H=33.0±5.3 (stat)±1.6 (syst)  pb. The measurements are compared to state-of-the-art predictions.Measurements of the total and differential cross sections of Higgs boson production are performed using 20.3 fb$^{-1}$ of $pp$ collisions produced by the Large Hadron Collider at a center-of-mass energy of $\sqrt{s} = 8$ TeV and recorded by the ATLAS detector. Cross sections are obtained from measured $H \rightarrow \gamma \gamma$ and $H \rightarrow ZZ ^{*}\rightarrow 4\ell$ event yields, which are combined accounting for detector efficiencies, fiducial acceptances and branching fractions. Differential cross sections are reported as a function of Higgs boson transverse momentum, Higgs boson rapidity, number of jets in the event, and transverse momentum of the leading jet. The total production cross section is determined to be $\sigma_{pp \to H} = 33.0 \pm 5.3 \, ({\rm stat}) \pm 1.6 \, ({\rm sys}) \mathrm{pb}$. The measurements are compared to state-of-the-art predictions